1. Field of the Invention
The present invention relates to an external sighting device mounted on an image pickup apparatus, various optical apparatuses, and the like to be used.
2. Description of the Related Art
It has been known that it is difficult to quickly and surely introduce a desired target of image pickup or observation into an image pickup visual field or an observation visual field because the image pickup visual field or the observation visual field is narrow, for example, when an image pickup target object (an object) present at a far distance is enlarged and subjected to image pickup using an image pickup apparatus such as a camera (including a digital camera and a digital video camera) or when an observation target object present at a far distance is enlarged and observed using various optical apparatuses for observation such as a telescope (including a field scope, a spotting scope, and binoculars).
Therefore, there have been proposed and put to practical use various means for enabling an object or an observation target object to be easily introduced into a visual field by attaching sighting devices of forms disclosed in, for example, Japanese Patent Application Laid-Open Publication No. H8-504029, Japanese Patent Application Laid-Open Publication No. 2001-500990, Japanese Patent Application Laid-Open Publication No. 2012-202573, and Japanese Patent Application Laid-Open Publication No. 2012-229844 to an image pickup apparatus, various optical apparatuses, or the like and using the sighting devices.